Although it is clear that the AIDS dementia complex (ADC) can precede CDC-criteria AIDS, it is not known whether there is a syndrome of mild mental affliction or reversible mental change in HIV-infected individuals without AIDS. Furthermore, it is not known whether there are early signs of neurological complications that are predictive of prognosis. The proposed study will provide information about the development of neurological complications among persons who are HIV antibody positive but who have not developed ARC or AIDS. The study population includes persons who are not in primary risk groups and offers an opportunity to study whether certain co-factors can be used to predict the development of neurological problems. The New York Blood Center (NYBC) is currently conducting a longitudinal panel study of blood donors who have been notified by the NYBC that they are HIV antibody positive. That study collects medical, serologic, behavioral and psychological information on donors at the time of notification and similar data twice a year after notification. The proposed Project would augment that study with a neurological and neuropsychological assessment two weeks after notification and at six-month intervals for a five-year period. All study participants will be given a 30-minute ADC- directed neurological and neuropsychological assessment which includes testing of sequential-alternation problem solving, verbal fluency, and fine motor control. Participants who have indications of impairment will be given a more complete evaluation. The study will assess the prevalence of ADC symptoms at baseline, describe the medical, serologic and immunological correlates of the ADC, prospectively monitor the development of symptoms and signs, and contribute data with Projects 1 and 2 to the Core, where analyses will attempt to develop multivariate models of the factors that are predictive of the development of ADC.